Background:Early metastasis of osteosarcoma (OS) is highly lethal and responds poorly to drug and radiation therapies. MicroRNAs (miRNAs) are a class of small noncoding RNAs that modulate gene expression at the post-transcriptional level. However, the detailed functions of specific miRNAs are not entirely understood. The aim of the present study was to investigate the role of miR-184 as a mediator of drug resistance in human osteosarcoma. Material/Methods:qRT-PCR was used to analyze the expression level of miR-184 in OS cell line U-2 OS and MG-63 treated with doxorubicin. MiR-184 agomir or miR-184 antagomir was transferred into cells to regulated miR-184. The target of miR-184 was predicted by TargetScan and confirmed by luciferase reporter assay. Bcl-2-like protein 1 (BCL2L1) expression was detected by Western blot. Cell apoptosis was determined by Annexin V staining and analysis by flow cytometry. Results:Doxorubicin induced time-dependent expression of miR-184 in OS cell line U-2 OS and MG-63. Luciferase reporter assay identified BCL2L1 as the direct target gene of miR-184. Furthermore, doxorubicin reduced BCL2L1 expression, which was reversed by miR-184 overexpression and further decreased by miR-184 inhibition in OS cells. In addition, miR-184 agomir reduced doxorubicin-induced cell apoptosis, whereas miR-184 antagomir enhanced apoptosis in OS cells, suggesting that up-regulation of miR-184 contributes to chemoresistance of the OS cell line. Conclusions:Our data show that miR-184 was up-regulated in OS patients treated with doxorubicin therapy and leads to poor response to drug therapy by targeting BCL2L1.
Advanced oxidation protein products (AOPPs) are recognized as novel markers of oxidative stress and contribute to various medical conditions, which are associated with secondary osteoporosis. However, little is currently known regarding the role of AOPPs in the development of secondary osteoporosis. As the commander cells of bone remodeling, osteocytes are involved in the pathogenesis of osteoporosis. The present study aimed to determine the cytotoxic mechanisms of AOPPs on osteocytic MLO-Y4 cells. The results demonstrated that treatment with AOPPs significantly triggered apoptosis of MLO-Y4 cells, in a dose- and time-dependent manner. Furthermore, exposure to AOPPs induced phosphorylation of c-Jun N-terminal kinases (JNK) and p38 mitogen-activated protein kinases (MAPK). Conversely, N-acetylcysteine inhibited the activation of JNK and p38 MAPK, thus suggesting that the AOPPs-induced activation of JNK/p38 MAPK is reactive oxygen species (ROS)-dependent. In addition, SB203580 and SP600125 suppressed apoptosis, but did not affect ROS production, following AOPPs treatment. Notably, AOPPs also induced a significant upregulation in the expression levels of sclerostin and receptor activator of nuclear factor kappa-B ligand (RANKL) in a JNK/p38 MAPK-dependent manner. These findings provide novel insights into the molecular mechanisms underlying AOPPs-mediated cell death, and suggest that modulation of apoptotic pathways via the MAPK signaling cascade may be considered a therapeutic strategy for the prevention and treatment of secondary osteoporosis.
Objective MicroRNA (miR)-22 plays crucial roles in malignant tumors and is involved in regulation of chemosensitivity. Additionally, altered expression of circulating miR-22 has been reported in various cancers. This study was designed to investigate plasma miR-22 expression in patients with osteosarcoma (OS) and determine its diagnostic, prognostic, and chemosensitivity prediction value. Methods Plasma miR-22 levels in 120 patients with OS and 120 healthy controls were detected by real-time quantitative reverse transcription PCR. Associations of plasma miR-22 expression with the patients’ clinicopathological features and prognosis were then assessed. Results Plasma miR-22 levels in patients with OS were significantly lower than those in healthy controls. Low plasma miR-22 levels were correlated with large tumor size, advanced clinical stages, positive distant metastasis, and poor tumor response to preoperative chemotherapy. Plasma miR-22 could discriminate OS patients from controls and distinguish patients with a good response to therapy from those with a poor response to therapy. Multivariate analysis revealed that low plasma miR-22 expression was a significant independent predictor of unfavorable prognosis. Conclusions Altered plasma levels of miR-22 might serve as a novel, noninvasive biomarker for OS diagnosis, prognosis, and chemosensitivity prediction.
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